Explosive



L. N. BENT EXPLosIvE Nov. 14, 1944.v

Filed Aug. 20, 1941 saV INVENTOR.'

BY magg Patented Nov. 14, 1944 EXPLOSIVE Ieavitt Hercules PowderCompany, W a corporation'of Delaware N. Bent, Wilmington, Del., assignorto ilmington, Del.,

Application August zo, 1941, lserial No. 407,512

Claims.

'I'his invention relates to 4improved blasting explosives and moreparticularly to explosives containing calcium nitrate as an ingredient.

Explosives, such as the commercial dynamites, usually are comprisedessentially of mixtures of nitroglycerin or similar liquid explosivenitric esters, one or more oxidizing,n salts, such as sodium, potassium,or ammonium nitrate, and

a carbonaceous or reducing material, such as/ wood pulp, .ground balsa,manioc meal, wood( flour, or the like. The inclusion of an oxidizingsalt in the dynamite compositions is most important as it affects thestrengthof the explosive and the oxygen balance of the admixture. It hasbeen long realized that calcium nitrate theoretically would providecertain denite advantages over the sodium, potassium, and ammoniumnitrate that are now used. Thus, for example, the oxygen balanceof thismaterial is superior to that of sodium nitrate. Further,l less energy isabsorbed by the calcium nitrate in' decomposing to produce a givenweight of oxygen.

However, calcium nitrate normally exists in the form of the hydratecontaining four molecules of water, and this water of crystallizationde- `creases the amount of oxygen available per unit weight, and theamount of energy available in the explosives which contain it as aningredient.

It is well'known that the hydrate of calcium nitrate can readily bedehydrated by melting the hydrate and boiling the resultant solutionwith the production of a flour-like material having a particle size ofabout twenty microns. In this finely divided state, the calcium nitrateis extremely hygroscopic and will quickly absorb moisture from the aireven when the relative humidity is quite low.. It has been proposed inU. S. Patent 1,865,382 to incorporate this nely divided material as aningredient in dynamite,

but such an ingredient tends to desensitize the powder especially whenit contains a relatively low percentage of nitroglycerin. In addition,the powder, in order to be useful, must be packed in .completelywaterproof containers and must be 4manufactured in an atmosphere ofcontrolled humidity, i. e., air-conditioned buildings.

The object of this invention is the production of blasting explosivecompositions of improved strength.

A further object o1 the invention is the production of dynamitscontaining calcium nitrate.

A still further object of the invention is the production 0f calciumnitrate in a granular form suitable for use in blasting explosives.

A further object of the invention is the production of a blastingexplosive containing granular free-flowing dynamite.

A still further object of the invention is to provide an explosivecontaining free-iiowing calcium nitrate having a screen size greaterthan about 150 mesh and preferably a material whichl will be retained ona 1D0-mesh screen.

Other and further objects of this invention will appear hereinafter.

The objects of the invention have been accomplished by providing calciumnitrate in a granular form which absorbs water vapor very slowly, andwhich when incorporated with the normal dynamite ingredients, provides ablasting explosive of improved strength. In more particular detail, theinvention comprises producing a granular free-flowing calcium nitrate byevaporating a calcium nitrate solution until a pasty mass is obtainedcontaining -95% calcium nitrate (anhydrous basis), which mass willconvert into a. crumbly mass. The crumbly mass is treated by a heatingor pulverizing action at a temperature not exceeding C. until there isproduced 'a granular material. This granular material, upon completecooling, is composed of compact, very hard granules which do not tend toabsorb moisture readily. In addition to this. method,'a granular calciumnitrate also may be prepared by completely evaporating all water ofcrystallization present in calcium nitrate and then admixing theresultant ne flour-like anhy- .drous material with a binder andgranumtmg the admixture either by rubbing it through a screen, kneadng,or similar operations.

, vlin the manufacture of -blasting explosives, such as dynamite, it ispreferable for the oxidizing salts used to -be in the form of moderatelycoarse free-owing granules. For example, the salts used may be held on a15G-mesh screen and preferably held on a 10D-mesh screen. It has beenfound that by preparing the calcium nitrate in accordance with thisinvention that a' granular material which will be held on a 100- mesh`screen can be produced and that this type granular material has a muchlower rate of moisture absorption than ilour-like calcium nitrate. Theinfluence ofthe particle size of the calcium nitrate on the rate of themoisture pickup is. shown in the attached graph. The graph shows-thetotal gain in weight of three samples of coarse material and a sample ofanhydrous flour-like material. Each sample was packed in parafned paperWrappers and exposed for a deiinite number of days to an atmos` phereheld at 70 F. and having a relative humidnitrate.

ity of 65%. llt will be seen that curve E is directed to anhydroushour-like calcium nitrate and that y dium nitrate and such replacementcan .be made on an approximately `1--l basis and will produce a dynamiteof .considerably higher strength than a dynamite containing an equalweight of sodium The percentage of calcium nitrate.

which may be used corresponds to the percentage of sodium nitrate thatmay be used and' in general will be between 5% and 65% of the .totalweight of the explosives. Calcium nitrate may be the only oxidizingagent in the explosive composition, or it may be mixed with sodiumnitrate, ammonium nitrate, ammonium perchlorate, or

l the like to obtain any particular characteristic which may be desired.Thev preparation of the dynamite is carried out by the methods which arestandard and well known in lthe explosive art.

In order to show the adaptation of the calcium nitrate of this inventionto use as an ingredient in dynamite compositions, .theollowlng examplesare given. It `Willbe noted from the examples that by substitutingcalcium nitrate for sodium nitrate an explosive of considerably higherstrength is obtained, and further, it will be noted that the examplesgiven cover each of the standard types of dynamite; Therefore, it `Willbe eppreciated that the calcium nitrate may -b'e used in any normaldynamite formulations.

Calcium nitrate sample 2 contained 1.5%"rosin which acted as a binderand produced the desired do naterdmpervious admirrture.

@i cium nitrate and the otherl containing flour-like calcium nitrate aregiven below.

A Tassa Il l@ Ingredients Per cent Per cent Nitrog1ynn l 20.0 20.Calcium nitrate granular 61. 4 Calcium nitrato iiour-like. 61. 4Carbonaceous material 18. 1 18. l g5 Chalk 0. 5 0. 5 154x 8cartridges/50 lbs-. 112 107 Gap propagation sensitlveness As msnui'inches.. 22 16 Y After5daysat120 F ...do. m 7 Detonation ratemeters/sec.. 3,361.; 3,200

ase'aeve ifcompared toAexplosives containing iine nourlike calciumnitrate. To show this dierence the composition and properties of twosamples of straight dynamite, one containing granular calln addition `tothe preparation t of the calcium nitrate by thermal treatment `vvithkneading or) by granulating by means oi' a binder, such as v:forexample, gum arabic, nitrocellulose, rosin or the like, it has also beenfound desirable to reduce the rate of moisture absorption of the calciumnitrate particles stilLfurther'by-coating the particles with a thin lmof a water-impervious mixture. Thus,

for example, the granular material may be treated with an admixture ofrosin, paramm and petrolatum having an approximate composition of 40,10, and i respectively by adding from 0.5-3%

of the rosin=paramn-petrolatum mixture to theA yas a revolving drumorother suitable method.

until each individual granule of calcium nitrate has coated thereupon avery thinllm of the The e'ect of the granular form. coating on `waterabsorption is shown in Table III. 'liners w l Example c straightammonium 4047 straight 207 gelatin @www 1%:6 dynamite ey'nsmitedyiiamite a B A B A B A B Nitwgiyesnn 20.0 20. o 11.0 11.0 sa o r9.0 20.o 20.0 Nitrocellulose 0. l. 0. l 0.2 0. 2 Ammonium mirata 13. Sodiumnitrate- 65. 47. 8 60. 3 Calcium nitrate l.- 00. 3 Calcium nitrate -s47. 8

ood ilour or other carboncceous material. 15. 7 11. 3 11. 2 14. 5 14. 5Sulfur 4.0 4.0 4.0 Chai 0.5 1.0 1.0 l 1.0 1.o

` 10o. 0 ico. 0 100.0. 100.0 100.0 100. 0 100.0 100 1% x 8 cartridges/50lbs 103 112 100 110 0S 104 81 Wt.strength(determinedwithballisticmortar) per cent.. 20 33 20 32 40 i8 20 Gappropagation sensitiveness .inches. 28 22 36 i0- 4 l Screen analysis ofthis sample: thru on 40 mesh-28%, thru 40 on tio-12%, thru 60 mesh-60%.f 2 Screen analysis of this sample: thru 20 on 40 mesh-32%, thru 40 onQ10-23%. thru 60 mesh-45%. A From the above table it will be observedthat TABLE m the calcium nitrate dynamite formulations show Moistureabsorption in 0pm dish, at 79 5%.,e1amaterially higher strength thanthose containing give humidity and Egect of coating sodium nitrate. Thestrengths were determined with a standard ballistic mortar and are ex- Iday 2 days pressed in terms of the equivalent straight nitroglycerindynamite. 4 p, m pe; m

The use of the granular calclummitrate of this Calcium nimm mum' mmM----1 2 Y Calcium nitrate granular coated 1 1.8 6 invention producesexplosives which are of im-- v This application of water-imperviouscoatings while highly desirable, and while giving a more water-resistantdynamite, is not essential since the granules of calcium nitrate are inthemselves somewhat water resistant, and when used in dynamiteformulations. produce dynamites that do not set into hard sticks orbecome insensitive due to water absorption for long periods of time.Other resin and waxy substances may be used as the coating, ifdesirable.

As previously indicated, the calcium nitra may be used for theformulation of all types of dynamite in admixture with a wide variety ofcommonly used ingredients. The calcium nitrate dynamite produced inaccordance with this invention may be used for all of the variouspurposes to which explosives are generally put and such dynamiteformulations will be found ex-. tremely eilicient. By virtue of the useof calcium nitrate in explosive formulation, the quantity of dynamiterequired may be reduced since the calcium nitrate content increases theweight strength of the explosive. Further. 'by the use of granularcalcium nitrate in dynamite formulations in ac-` cordan'ce with thisinvention, desirable cartridge count may be obtained and various bulkand weight strengths produced in explosive compositions which mayotherwise be diiilcult to obtain with sodium nitrate.

What I claim and desire to protect by Letters Patent is:

1. A blasting explosive comprising an admixturecontaining a liquidexplosive nitric ester. a carbonaceous material, and calcium nitrate,said calcium nitrate characterized by being granular, free-ilowingparticles of a size that substantially all particles will be retained ona 1D0-mesh screen.

2. A blasting explosive comprising ln admixture a liquid explosivenitric ester and calcium nitrate. said calcium nitrate beingcharacterized by a granular. free-flowing form and having a screen sizesuch that all particles are retained on a 10D-mesh screen.

3. A blasting explosive comprising in admi!- ture nitroglycerin, acarbonaceous material,l and 4. A blasting explosive comprising inadmixture a liquid explosive nitric ester, a carbonaceous material. anda granular free-flowing calcium nitrate having a screen size betweenaboutv 9 and l0-mesh whereby the rate of Water absorption of saidcalcium nitrate at 70 F. and 65% relative humidity is not more than .1%by weight per day.

5. A dynamite composition 20% nitroglycerin, 18% carbonaceous material,calcium nitrate and .5% antacid, said calcium nitrate beingcharacterized by a granular free-flowing form and a screen size ofbetween 9 and 40mesh.V

6.1A dynamite composition comprising nitroglycerin about 11%, ammoniumnitrate about 13%, calcium nitrate about 55%, carbonaceous materialabout 15%, and antacid about .5%, said calcium nitrate beingcharacterized by a granular free-flowing form and having a screen sizebetween about 9 and about 40-mesh.

7. A blasting explosive comprising an admixture containing a liquidexplosive nitric ester, a carbonaceous material, and coated calciumnitrate, said calcium nitrate having a water-irnpermeable coating on thesurface and characterized by being granular, free-flowing particles of asize that substantially all particles will be retained on a 1GO-meshscreen.

8. A blasting explosive comprising in admixture nitroglycerin, acarbonaceous material, and granular free-iiowing calcium nitrate coatedwith a water-impermeable material, and characterized by a screen sizebetween about 9 and Aiii-mesh.

9. A blasting explosive comprising in admixture nitroglycerin, acarbonaceous material, and granular free-flowing calcium nitrate coatedwith a thin iilm comprising an admixtureof a resin and a waxy substance,and characterizedby a screen size betweenv about 9 and 40-mesh.

10. A blasting explosive comprising in admixture nitroglycerin, acarbonaceous material, and granular free-flowing calcium nitrate coatedwith a thin illm comprising an admixture of rosin, parailn andpetrolatum, and characterized by a screen size between about 9 and40-mesh.

LEAVITT N. BENT.

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